Electronic combination lock with PIC MicrocontrollerThis is an electronic combination lock to use with an outdoor gate. The functionality is implemented in software. It turns on a relay (usually to open a door) for a few seconds if someone enters the valid code. This relay can operate a power-to-open type electric strike with a shorting contact or a power-to-hold type electromagnetic lock with a breaking contact (we need the relay because these locks usually work with AC, not DC). The code can be changed any time after entering the current code.

Electronic combination lock with PIC Microcontroller
at jap.hu
Website

Electronic combination lock with PIC Microcontroller